Wireless communications have been used on the battlefield since the first world war and are critical for staying in touch with deployments near and far. Word today is that Hezbollah hacked Israeli communications during the battles in Israel and Lebanon in August 2006.
Using technology most likely supplied by Iran, special Hezbollah teams monitored the constantly changing radio frequencies of Israeli troops on the ground. That gave guerrillas a picture of Israeli movements, casualty reports and supply routes. It also allowed Hezbollah anti-tank units to more effectively target advancing Israeli armor, according to the officials.
My guess is that they weren’t able to decipher the communications at all; Israel is host to some of the top cryptographic minds and companies. However, just by tracking the transmissions they learned enough about what was going on to prepare themselves better.
It’s easy to fall victim to believing too much in the resilience of your cryptographic algorithms and forget that radio silence is still the best way to keep your communications hidden from the enemy.